Detector device for haemodialysis unit

ABSTRACT

The invention relates to a device for detecting blood loss from an electrolytic solution used for haemodialysis. The device comprises a cylindrical chamber having a window in the lower part of each end wall and inlet and outlet ports at the top. The windows are coupled to respective light guides which transmit light to a photodetector from a light source through the chamber through which the electrolytic solution is passed during the dialysis. Any change in the amount of light absorbed by the solution indicates blood loss from the dialysis unit and is detected by the photosensitive device which is connected to a detection circuit which provides an alarm indication when the variation of the absorption exceeds a predetermined threshold value.

ilited States Patent Diamanti et al. 1 Oct. 2, I973 [54] DETECTOR DEVICE FOR HAEMODIALYSIS 3,518,437 6/l970 Riggs 250/218 X UNIT 3,325,724 6/1967 Aiken 250/205 X V m .4 m2 do- 3,606,539 9/1971 Polanyietal. 356/39 75] Inventors: Sergio Diamanti,Turin;Enni0 Den! Pino Totmesel Antonio Primary Examiner-Walter Stolwein vel'celloneaTunn, of Italy Attorney-Riehard C. Sughrue et al.

[73] Assngnee: Sorln S.p.A., Sluggia, Italy ABSTRACT [22] Filed: June 1972 The invention relates to a device for detecting blood [2i] Appl. No.: 265,370 loss from an electrolytic solution used for haemodial ysis. The device comprises a cylindrical chamber having a window in the lower part of each end wall and [30} Foreign Application Priority Data inlet and outlet ports at the top. The windows are cou- June 30, I97] Italy 69222 A/7l pled to respective light guides which transmit light. to

222W a photodetector from a light source through the cham- [52] US. Cl 250/565, 356/39, 250/227 through which the electrolytic Solution is passed [51] IIIL CI. G01 21/26 during the dialysis y change in the amount of light [58] Field of Search 250/218, 205, 227; absorbed by the Solution indicates blood loss from the I 356/39-42 dialysis unit and is detected by the photosensitive device which is connected to a detection circuit which [56] References C'ted provides an alarm indication when the variation of the UNITED STATE PATENT absorption exceeds a predetermined threshold value. 3,307,447 3/1967 Carleton 'et al. 250/218 X 2,835,252 5/1958 Mauchel 356/39 x 3 2 Dm'mg F'gum 1 DETECTOR DEVICE FOR HAEMODIALYSIS UNIT BACKGROUND OF THE INVENTION The present invention relates to a device capable of measuring the haematic losses in an electrolytic solution used in haemodialysis.

Artificial substitution of the renal function is known in the art and is normally effected by arrangements which provide for the transfer of toxic uraemic products by means of dialysis of the blood. In these arrangements the blood of the patient is passed around a circuit including suitable dialysers. In these the blood is separated by the electrolytic solution through semipermeable membranes of different shape and geometry, generally composed of regenerated cellulose film or suitable plastic substances. One characteristic of films employed for this purpose is the minimum thickness (12 18 micron) which is such that rupture of the membrane is likely; moreover small losses from the haematic circuit inevitably occur due to the presence of microscopic holes in the membrane itself, both of these lead to blood loss from the haematic circuit.

Blood losses from the haematic circuit are particularly serious for those patients who are suffering from uraemia, due partly to the tendency towards anaemia which is characteristic of the uraemia syndrome, and partly to the increased duration of each dialysis session. Even very small losses through microscopic holes in the membrane, for instance of the order of 0.05 cm of blood per minute, lead, at the end of a dialysis session, to a total loss which may be greater than 50cm. It is thus evident that in the treatment of chronic uraemia it is important to be able to detect any haematic loss as soon as possible.

There are some devices known in the prior art which can detect the presence of red globules in the electrolytic solution used for the dialysis. Such devices generally operate to detect changes in the absorption of light in the electrolytic solution caused by the presence of red globules. Such changes in the absorption are recorded by photosensitive circuits which are linked to signalling devices which operate to indicate when blood losses reach an unacceptable level.

The main disadvantages of such prior art devices are their poor sensitivity, or the instability of the measuring system when adjusted to the highest sensitivity, and the variation of sensitivity with time, due to the progressive obscuration of the windows of the recording device caused by deposits of salts precipitated from the electrolytic solution.

OBJECT OF THE INVENTION The object of the present invention is to provide apparatus in which both the abovementioned disadvantages are at least reduced and preferably substantially eliminated.

SUMMARY OF THE INVENTION According to the present invention, there is provided a device for detecting haematic losses in an electrolytic solution being used for haemodialysis, comprising a tion, and circuits connected to the photosensitive element sensitive to variations of its output signal and operative to provide a signal when the variation exceeds a predetermined threshold value, characterized in that between the source of light and the associated window, and between the photosensitive element and the associated window there are provided respective light guides operable to direct the light to or from the associated window.

Various other features and advantages of this invention will become more apparent during the course of the following description with reference to the accompanying drawings which is given purely by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial section of a measuring chamber forming part of the embodiment of this invention; and

FIG. 2 is a diagrammatic illustration of the electronic circuit used in conjunction with the measuring chamber illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is shown a tubular sleeve 10 of rigid material, for instance metal, which is anchored to a base 12 by screws 14, I6. The chamber is shown in FIG. 1 in a normal orientation and reference herein to upper and lower etc., will be construed as referring to the chamber when in the orientation shown in the drawing. The sleeve 10 is provided with an inlet orifice I8 and an outlet orifice 20 for connection to haemodialysis apparatus (not shown) so as to allow the dialytic solution in the apparatus to flow through the measuring chamber.

The ends of the sleeve 10 are closed by plates 22, 24

of a transparent material which are sealed to the ends by means of sealing rings 26, 28 located in respective annular grooves 30, 32 in the ends of the sleeve 10. Over the transparent plates 22, 24 there are respective opaque plates 34, 36 which have apertures 38, 40 in which are housed the ends of respective optical guides 42, 44. The apertures 38, 40 are formed in the lower half of the opaque plates 34, 38 so that any air bubbles which may pass through the chamber will not pass between the apertures 38, 40 due to their tendency to remain in the top half of the chamber. This ensures that spurious signals causing possible false alarms are not generated by the apparatus due to the presence of such air bubbles.

The sleeve 10 is formed with two reference grooves 46, 48 for locating the plates 34, 36 in the correct orientation when the apparatus is being assembled.

To the plates 34, 36 are soldered respective protection cups 50, 52 so as to create respective protected chambers 54, 56 adjacent the plates, within the respective cups.

The ends of the sleeve 10 are formed with screw threads so that the assembly comprising the plates 34, 36 and the cups 50, 52 can be secured thereto by means of threaded rings 58, 60. In the chamber 56 an axially oriented rod 66 mounted between the plate 36 and the bottom (not shown) of the cup 52 carries a bracket 68 to which there is fixed, by a bolt 70, a lampholder 72 for lamp 74, supplied with current by conductors 76 from a connector 78.

A similar axial rod 80 is also mounted in the chamber 54 between the plate 34 and the bottom (not shown) of the cup 50. A bracket 82 carried by the rod 80 supports a photosensitive assembly 84 comprising two phototransistors in a Darlington circuit, protected by a cover 86 on the outer end of the optical guide 42. Output conductors 88 carry signals generated by the photosensitive assembly 84 to external detector circuits through connectors 89, 90.

This construction of the measuring chamber described above ensures that the transparent windows 22, 24 can be very easily dismantled for cleaning, inspection, or the like, and ensures that the geometry of the chamber is maintained upon reassembly without requiring adjustment.

Experiments carried out have demonstrated that, other parameters being equal, it is possible to obtain a sensitivity which is times greater from a chamber furnished with optical guides such as those described above than from a chamber without such guides. This allows the use of a lower power supply for the lamp 74, thus extending its life. Moreover the electronic detecting system is less critical, because only a small amplification of the signal from the photosensitive device 84 is required.

To avoid loss of sensitivity due to a gradually increasing opaqueness of the windows 22, 24 of the measuring chamber resulting from deposition of salts as discussed above, use is made of an electronic circuit provided with an arrangement for detecting the slight variations of light transmission attributable to such deposition and for ignoring such variations so that generation of false alarms from this effect can be avoided.

FIG. 2 is a block diagram of a preferred embodiment of a supply and signalling circuit for use with the chamber described in relation to FIG. 1. The lamp 74 is supplied from a stabilised power supply unit 100. The photosensitive assembly 84 is connected to a potentiometer 102 the cursor 104 of which is connected to the input of a voltage amplifier 106. Adjustment of the potentiometer 102 thus effects adjustment of the sensitivity of the apparatus. The output of the amplifier 106 is connected through conductors 108, 110 to a first comparator 112 and to a second comparator 114 respectively. The comparators have respective regulation potentiometers 116, 1 18. The output of the first comparator 112 is connected to a circuit 120 for excitation of a pre-alarm lamp 122. The output of the alarm comparator 114 is connected to a circuit 124 for excitation respectively of a visible alarm indicator 126, an audible alarm indicator 128 and a relay 130 for detachment of the haematic pump (not shown) of the haematic circuit.

The threshold value of the first comparator 112 is selected so that the indication supplied by it will indicate a variation of transmission of the light attributable either to slight opacity of the windows of the measurement chamber or to a blood loss so small as not to justify suspension of the treatment. However the prealarm indication supplied by the indicator 122 is useful inasmuch as it relieves the supervising personnel of the necessity of performing a check on the measuringv chamber to determine whether its windows are clean before starting each dialysis session, it being only necessary to adjust the potentiometers 116 and 118 to compensate for any slight opacity of the windows at the commencement of the dialysis session.

Experiments have shown that the apparatus described above is capable of detecting blood losses which are much lower than the visible limits with direct supervision. This is especially important in that any leaks in the dialysis apparatus, evey of very small amounts, can be detected at an early stage so that any necessary precautionary or corrective measures can be taken in good time. The apparatus automatically operates in the event of blood loss above the predetermined threshold to stop the blood pump, and therefore the dialysis, to avoid the danger of unacceptable blood loss even in the absence of supervision.

The apparatus described above has been clinically tested and found satisfactory with 430 hours practical operation in a haemodialysis circuit of a kidney of Kiil."

It will be appreciated that only one particularly preferred embodiment of this invention has been illustrated, purely by way of example, and that numerous variations or modifications, may be made thereto without thereby departing from the scope of the invention.

In particular, for the purpose of increasing the sensitivity of the device without increasing the power supply to the lamp 74, the lamp may be provided with a parabolic reflector so as to increase the luminous flux in the direction of the light guide. Also the illustrated embodiment of the detecting circuit is given by way of example, and thus many variations are possible, such as the provision of different types of indication, in relation to the particular requirements of different circumstances.

We claim:

1. A detector device for detecting blood loss in an electrolytic solution being used for haemodialysis in a dialysis unit, said detector comprising:

a housing defining a chamber;

a first means comprising an inlet and an outlet means in communication with the upper part of said chamber and connecting said chamber to said dialysis unit, whereby said electrolytic solution can flow there through;

first and second light transmitting windows mounted in said housing at opposite ends thereof;

first and second light transporting and channelization means mounted in said housing adjacent to said first and second light transmitting windows, respectively, on the sides thereof remote from said chamber, each of said first and second light transporting and channelization means comprising an opaque plate having an aperture formed therein in the lower part thereof and a light guide mounted in said aperture, whereby any air bubbles which may pass though said chamber will not pass between said light guides;

a light source adjacent the end of said light guide in said first light transporting and channelization means remote from said chamber, whereby light from said light source may be guided through said light guide into said chamber;

photosensitive means adjacent the end of said light guide in said second light transporting and channelization means remote from said chamber, whereby light transmitted through said chamber and through said second light transmitting window may be guided through said light guide to said photosensitive means; and

detector means coupled to said photosensitive means, said detector means providing an alarm ends of said sleeves and threaded rings holding said windows in place on 'said sleeve.

3. A detector device as claimed in claim 1 wherein said light guides comprise blocks of transparent material the cross-sectional area of which increases in a regular fashion from the end thereof remote from said chamber to the end thereof nearer to said chamber. 

1. A detector device for detecting blood loss in an electrolytic solution being used for haemodialysis in a dialysis unit, said detector comprising: a housing defining a chamber; a first means comprising an inlet and an outlet means in communication with the upper part of said chamber and connecting said chamber to said dialysis unit, whereby said electrolytic solution can flow there through; first and second light transmitting windows mounted in said housing at opposite ends thereof; first and second light transporting and channelization means mounted in said housing adjacent to said first and second light transmitting windows, respectively, on the sides thereof remote from said chamber, each of said first and second light transporting and channelization means comprising an opaque plate having an aperture formed therein in the lower part thereof and a light guide mounted in said aperture, whereby any air bubbles which may pass though said chamber will not pass between said light guides; a light source adjacent the end of said light guide in said first light transporting and channelization means remote from said chamber, whereby light from said light source may be guided through said light guide into said chamber; photosensitive means adjacent the end of said light guide in said second light transporting and channelization means remote from said chamber, whereby light transmitted through said chamber and through said second light transmitting window may be guided through said light guide to said photosensitive means; and detector means coupled to said photosensitive means, said detector means providing an alarm output when the output from said photosensitive means changes by more than a predetermined threshold value.
 2. A detector device as claimed in claim 1 wherein said housing comprises a cylindrical sleeve and said first and second light transmitting windows are mounted in said sleeve at opposite ends thereof and further comprising sealing rings located between said windows and the ends of said sleeves and threaded rings holding said windows in place on said sleeve.
 3. A detector device as claimed in claim 1 wherein said light guides comprise blocks of transparent material the cross-sectional area of which increases in a regular fashion from the end thereof remote from said chamber to the end thereof nearer to said chamber. 